J/MNRAS/474/4396 MASIV Survey. IV. Radio AGNs variability (Koay+, 2018)
The MASIV Survey.
IV. Relationship between intra-day scintillation and intrinsic variability
of radio AGNs.
Koay J.Y., Macquart J.-P., Jauncey D.L., Pursimo T., Giroletti M.,
Bignall H.E., Lovell J.E.J., Rickett B.J., Kedziora-Chudczer L., Ojha R.,
Reynolds C.
<Mon. Not. R. Astron. Soc., 474, 4396-4411 (2018)>
=2018MNRAS.474.4396K 2018MNRAS.474.4396K (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Radio sources
Keywords: scattering - galaxies: active - galaxies: jets - quasars: general -
gamma rays: galaxies - radio continuum: galaxies
Abstract:
We investigate the relationship between 5GHz interstellar
scintillation (ISS) and 15GHz intrinsic variability of compact,
radio-selected active galactic nuclei (AGNs) drawn from the
Microarcsecond Scintillation-Induced Variability (MASIV) Survey and
the Owens Valley Radio Observatory blazar monitoring program. We
discover that the strongest scintillators at 5GHz (modulation
index, m5≥0.02) all exhibit strong 15GHz intrinsic variability
(m15≥0.1). This relationship can be attributed mainly to the mutual
dependence of intrinsic variability and ISS amplitudes on radio core
compactness at ∼100µs scales, and to a lesser extent, on their
mutual dependences on source flux density, arcsec-scale core dominance
and redshift. However, not all sources displaying strong intrinsic
variations show high amplitude scintillation, since ISS is also
strongly dependent on Galactic line-of-sight scattering properties.
This observed relationship between intrinsic variability and ISS
highlights the importance of optimizing the observing frequency,
cadence, timespan and sky coverage of future radio variability
surveys, such that these two effects can be better distinguished to
study the underlying physics. For the full MASIV sample, we find that
Fermi-detected gamma-ray loud sources exhibit significantly higher
5GHz ISS amplitudes than gamma-ray quiet sources. This relationship
is weaker than the known correlation between gamma-ray loudness and
the 15GHz variability amplitudes, most likely due to jet opacity
effects.
Description:
Richards et al. (2014MNRAS.438.3058R 2014MNRAS.438.3058R, Cat. J/MNRAS/438/3058) in their
paper present the 15GHz variability amplitudes of ∼1500 blazars
based on 4yr of monitoring by the OVRO 40m telescope. Each source
was observed at a cadence of two flux measurements a week between 2008
January to 2011 December.
A total of 178 in our MASIV sample are also in the original
radio-selected OVRO 15GHz monitoring sample.
The list of 178 sources is presented in Table 1, together with the
variability amplitudes of the sources and other source properties.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 110 178 List of common sources found in both the MASIV sample
and the OVRO 15 GHz blazar monitoring program
(Richards et al. 2014MNRAS.438.3058R 2014MNRAS.438.3058R), their
intrinsic properties, and variability characteristics
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See also:
II/249 : WHAM Northern Sky Survey, V-1.1 (Haffner+, 2003)
J/MNRAS/438/3058 : 15GHz variability of γ-ray blazars (Richards+, 2014)
J/MNRAS/452/4274 : Angular sizes of AGN cores at 2-43GHz (Pushkarev+, 2015)
J/ApJ/689/108 : MASIV survey. II. First four epochs (Lovell+, 2008)
J/ApJ/767/14 : MASIV survey, III. Optical identifications (Pursimo+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name (JHHMM+DDMM, J2000),
CGRaBS JHHMM+DDMM in Simbad
13- 17 F5.3 --- m5 5GHz modulation index (1)
20- 24 F5.3 --- e_m5 Error in m5 (1)
27 I1 --- Nep Number of epochs variable in the
MASIV survey (1)
30- 34 F5.2 Jy F5GHz 5GHz flux density (1)
37- 41 F5.3 --- m15 15GHz modulation index (2)
44- 48 F5.3 --- E_m15 Upper error in m15 (2)
51- 55 F5.3 --- e_m15 Lower error in m15 (2)
58- 62 F5.2 Jy S15GHz 15GHz flux density (2)
65- 68 F4.1 Ry IHa Halpha intensity (Rayleighs) (3)
71- 74 F4.2 --- z Redshift (4)
76- 80 F5.2 mas theta2 ? 2GHz core size (5)
83- 86 F4.2 mas theta5 ? 5GHz core size (5)
89- 92 F4.2 mas theta8 ? 8GHz core size (5)
95- 98 F4.2 mas theta15 ? 15GHz core size (5)
101-104 F4.2 mas theta24 ? 24GHz core size (5)
107-110 F4.2 mas theta43 ? 43GHz core size (5)
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Note (1): from Lovell et al. 2008ApJ...689..108L 2008ApJ...689..108L, Cat. J/ApJ/689/108
Note (2): from Richards et al., 2014MNRAS.438.3058R 2014MNRAS.438.3058R, Cat. J/MNRAS/438/3058
Note (3): from Haffner et al., 2003ApJS..149..405H 2003ApJS..149..405H, Cat. II/249
Note (4): from Pursimo et al. 2013ApJ...767...14P 2013ApJ...767...14P, Cat, J/ApJ/767/14 and
Pursimo et al. in prep.
Note (5): from Pushkarev & Kovalev, 2015MNRAS.452.4274P 2015MNRAS.452.4274P, Cat. J/MNRAS/452/4274
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History:
From electronic version of the journal
References:
Lovell et al., Paper I 2003AJ....126.1699L 2003AJ....126.1699L
Lovell et al., Paper II 2008ApJ...689..108L 2008ApJ...689..108L, Cat. J/ApJ/689/108
Pursimo et al., Paper III 2013ApJ...767...14P 2013ApJ...767...14P, Cat. J/ApJ/787/14
(End) Patricia Vannier [CDS] 04-Mar-2021